OBJECTIVES: The objectives of the research are to synthesize moderate molecular weight polymers containing fluorinated side chains that also contain unsaturated groups available for crosslinking and to polymerize these polymers into a hydrophobic composite restorative material. Promising hydrophobic composites will be evaluated on the basis of their physical and mechanical properties including wear. The most promising hydrophobic composites will also be evaluated for capillary penetration between tooth structure and the composite by neutron activation analysis. Goals for the current year include continued development of fluorine-containing polymers, already synthesized into more successful composites by incorporating more and different fillers and a greater variety of fluorinated monomers to control the vixcosity and hydrophobicity. The capillary penetration of fluids around restorations will be evaluated on extracted teeth using the experimental fluorinated polymers. Additional fluorine-containing polymers will be produced with longer side chains in order to further increase the hydrophobicity.